Tuning means for electron discharge devices



April 1948. w. w. RIGROD TUNING MEANS FOR ELECTRON DISCHARGE DEVICES Filed Sept 21 MM E/GEOD ATTORNEY Patented Apr. 20, 1948 TUNING MEANS FOR ELECTRON DISCHARGE DEVICES William W. Rigrod, Bloomfield, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa.,

a corporation of Pennsylvania Application September 21, 1943, Serial N0. 503,189

3 Claims.

This invention relates to electron discharge devices and is exemplified in the present disclosure as embodied in a device available in the market under the trade name of Klystron" which is one form of utilizing a beam of electrons and with a resonant cavity for producing the high frequency oscillation.

Due to the wide range of ambient temperatures C. to +60 C.) under which a "Klystron must operate, for instance as a local U. H. F. oscillator, its copper parts undergo pronounced thermal contractions and expansions which cause the operating frequency to vary considerably. A typical test showed a frequency shift of 19 megacycles per second. A "Klystron utilizes a hollow body resonator having a constricted gap between the hollow thereof and the passageway for the electron beam. This gap spacing is highly critical in determining the resonant frequency of the device, as the spacing determines most of the distributed equivalent capacitance of the cavity. In fact, advantage is taken of this critical spacing by varying it slightly for tuning purposes. Experiment and use have shown that the constriction varies in size or spacing as the result of variation in ambient temperature. Increase in ambient temperature leads to expansion of parts which control the gap opening of the constriction decreasing the gap opening with a corresponding increase in the equivalent capacitance of the cavity and hence a decrease in the operating frequency of the Klystron. In its most general aspects, therefore, the invention seeks to overcome the detrimental effects of ambient temperature in a device of the character indicated.

Likewise broadly considered, an object of the invention is to provide compensating means for de-tuning effects of external temperature changes in a beam-type electron discharge device.

More specifically, an object of the invention ultra high frequency device g is to maintain the gap opening of the constric tion of a beam-type electron discharge device substantially constant under external or ambient temperature variations of a considerable range.

Another object of the invention is to provide a. compensatin means for de-tuning effects of temperature changes in a beam-type electron iischarge devicewhich is applicable to such devices as heretofore manufactured.

A further object of the invention is to proide a temperature compensating strut.

A still further object of the invention is to a body of revolution about an axis.

the electron beam therethrough from strut which may be readily substituted of a present-day non-compensating provide a in place strut.

Other objects of the invention will appear as the description progresses, both by direct recitation thereof and-by implication from the context.

Referring to the accompanying drawing .in which like numerals of reference indicate the same parts in both views:

Figure 1 is a side elevation of an electron discharge device of the character indicated showing the invention incorporated therein; and

Figure 2 is a plan of the same.

In the specific embodiment of the invention illustrated in said drawing, the reference numeral l0 designates an electron discharge device of the beam type, and more specifically a K13!- stron and shown as constructed in general as The usual structural features of such a device comprise a cathode II, in a plane normal to the axis, at a distance from which is disposed a reflector l2 also transverse to the axis, said axis passing through the centers of both the cathode and refiector. In the region intervening between the cathode and reflector is a hollow resonant chamber l3 the opposite walls of which transverse to and around the axis are perforate for passing the cathode to the reflector and back again into the.resonator. The perforate parts of the walls, for want of a better term, have been identified in the art as grids, and accordingly in the order of .nearness to the cathode will be here identified as the near grid l4 and far grid l5 of the resonator. Between the cathode and said near grid M of the resonator is a focusing grid IE, it being situated as close as electrically and mechanically feasible to the cathode. This focusing grid l6 and said near grid M are mounted in opposite ends of a tube or collar H the end of which at the focusing grid having an outwardly directed flange I8 therearound. Said collar is usually of copper the coefiicient of expansion of which is 17 10- inches per inch per degree centig-rade. Onthe outside of said collar and shown approximately midway of the length thereof, is secured, vacuum tight, a flexible diaphragm I!) which constitutes a flexible end wall for the resonant chamber for tuning purposes. The lower end of the collar below said flexible diaphragm is exposed to effects of exterior temperatures. The opposite end wall 20 of the resonant chamber is shown as rigid and fixed, within the resonant chamber and in the plane of the far grid I 5. The fixed end wall is secured within a central hollow in a circular plate or ring 2|. Collar I! to which the flexible wall of the resonator is attached has its flange l8 seated in a central socket in another circular plate or ring 22. A cylindric copper wall :11 fixed endx'wallifl and outer periphery ofthe flexible diaphragm l9 completing the resonator enclosure. Said plates or rings 21 and 22 are sub-' stantially parallel and equal in size. springs 23 have their opposite endshookedfinto the two plates next their peripheries thereby tending to draw said plates: :towardzeach other; and interposed midway betweenrther; springsa parallel thereto and perpendicular totheplates are struts 24 for holding the plates. apart. Ac-' cording to the present showing, three struts are provided all of except that two seat directly in sockets in the movable plate 22 whereas the. third one seatsin a socket in tuning-lever-Zii carried-by said plate. Description of one strut will accordingly suffice for all.

Construction of strut 2e represents anessential feature-of the present invention. As shown; saidstrut comprises essentially two members of which one, called for oonveniencetheadjustingmember or spacer :2 6; is deeply recessed longitudinally to loosely receive the other memben vforrconvenience referred'to herein1as-prop;2'l. The body portion of said prop is elongated; and has its oppositeends recessed to each receivertherstem port-ion, o t ashouldered pin 28 theqouter: endofwlrichhas a rounded tip -with the-shoulder situated between the-stem andtip and extendingglaterally so as-to ride srotatablyson the i end of theib ody portion of Tension which are of like construction.

extends" between the lfiml of ,the' e the-iprop. At a'given temperature the-;prop is offixed. length, but preferably has:its;-body-portion of a material. highly responsive to .heat "changes. and having; considerable expansion":with :rising corresponding: contraction with lowering temperatures. The-zoverall length temperatures and a ofrsaidprop'accordinglyyaries with theftemperature. Several materials :have been'zioundrsatisfactoryfortuse'in therconstruction of this prop; namely; Duralumin as l'lS T, brass alloy 240 off the-r-Revere" Co.

said to contain approximately 60%: copper 'and 40 zinc, and 'W-esting-houseralloy known in the trade. as Cupalloy. have coefficients of thermal expansion (unsubstantially 24 l0- 21 l0- and .lilx-lilr respective ly,- andiniany'eyent' greater than thecoeilicient of.

expansion of-the collar l1.

The adjusting member 261s preferably offamaterial having lessexpansionthanpropxfl forr'a given: rise of temperature: Satisfactorymaterials for this member have been found to-be either "of two'materials, namely a'material available inthet market underzthe trade name Kovarf having :a

coefiicient of thermal expansion of substantially 4.7 -1()- and-azmaterial available 'in the marketidentified by": the:- maker These several 1 materials under-qthe :tradeaname Nilvari"having fa coeflle cient? of. thermal" expansion of" substantially IX 10*; Thesematerials are alloysessentially of 1 iron, nickel andvcobalt; It is thefipurposeto use? a satisfactory material f or this: spacer havingras= little expansion as possible.

By selecting for the adjustingsmember 26a ma terial. as indicated of low thermal expansivity, and for "the prop 2T a material of-high' thermal expansivity, the? net efiect of: an increase in teme perature is to increase the distance between the" two mounting plates or rings 2 f and 22'." It is rundueto externalchanges of temperature effective thereon. Th'usgas-collar ll expands due to rise in temperature thereby tending to move the near grid M closer to far grid 15, the heat also effective upon the strut produces a substantially equal net expansion therein, thereby separating the plates 2 I, 22 a distance comparable to and compensatin forexpan'sion'of the collar and thus automatically maintaining; a substantially constant spacingiof the grids:

Theradjusting member is shown as :finelyscrew" threaded :on its-exterior at its: end portion-:passa ingthrough. the plate which" is "corresponding-1y threadedqto receiveand holdsaid member; The? several adjusting members are brought to prop'ers' position during manufacture and-locked :there'at by a lock:nut 29. 011thejEsaid"memBer JneXt the plate. Thissetting ordinarily remains fixed after release of the' device from: theifactory. The. rounded tips of 'two' of .theeprops seat in hollows." orsockets-therefor'irr the movabl'e plate: The

rounded tip of thefthird: propi-seats-in a'like'sockct-i 39 in tuninglever 25 which isliulcrumed at 3 I; A micrometer screw (not shown) is employed? in:

practice-to swing this lever 'andrther'eby changa the grid spacing for tuning. purposes; but-without disturbing thetfunctioningzof the prep for "auto matic' compensation fora-heat expansion of collar ll.

While in the .foregoing description: certain 'niae terials' and specifici arrangement of part's::have

been recited; otherimaterials having similar prop-*- erties andptherarrangements having equir'ralerft: utility may be employed. In'this connectionit may be pointed .out that the prop .materialmust possess, not *merelyhigh thermal? expansivity to":

compensate for the collar: expansion; but: mustfurthermore have sufiicient. mechanical strength to resist" buckling. under: combined compressive and shearing stresses to which it"is -=subjected in.

use:

In? order to prevent permanent deformation" under stressor creep of theiprops; .thepi'nsin the ends thereof are. preferably employed"and? these pins arepf a hardmaterial; such asz-stain less steel and have the rounded-tipsrfor ermitting movement 'of'th'etip in the socket. Theaprop: as a Wholeis .preferablyWaged priorcto installationw.

by repeated heating and cooling over the entire:

temperature range of operation; this :preca-ution having been found" advantageousifor: preventing any permanent deformation, however-slight, of.

the prop :in use;

The -mounting" of the adjustingamemberaaor." spacerby means of threaded engagement withzthe plateandsecuringb'y a lockcnut is;superior to a welded; brazed, soldered or other permanent. or fixed; assembly, because: it'permits :convenientf installation after theKlystron"i has been assem bled; exhausted and sealed: oil; becauserit I admits of factory tuning: with'thevgrids' perfectIyspan'- allel; becausemf. its simple "and cheap const'ruc tion; and because it permits the use of struts of various lengths for any desired grid spacing to be applied in manufacture interchangeably. The latter advantage is of great value in providing equally efiicient temperature compensation at widely different operating frequencies, as well as permitting the use of struts of different materials and of different thermal expansivities.

The strut of the present invention is readily applied to Klystrons of prior art construction without materia1 change of the Klystron parts other than the struts. These struts constitute broadly automatic temperature compensated tuning means and have been found from test to maintain substantially constant or perfect frequency stability with ambient temperatures within the range encountered in use approximately from 40 C. to +60 C.

I claim:

1.. An electron discharge device having a hollow body resonator with a fixed end wall, said resonator having a movable collar as a part thereof, said collar having an end thereof within the resonator spaced from and opposing a part of the fixed wall of said resonator and forming thereby a constriction, said collar having an end external of the resonator, plates respectively carrying said external end of the collar and said fixed part of the resonator, springs coupling and tending to draw said plates together and lessen the spacing between said fixed part of the resonator and the collar, and struts secured to one of said plates opposing the spring action and keeping said fixed part and collar spaced, said struts having greater coefiicient of expansion than said collar and automatically compensating for expansion of the collar due to heat in use and thereby maintaining the said spacing between said fixed part and the collar substantially constant under varying heat conditions encountered in use of the device.

2. An electron discharge device having a hollow body resonator with a fixed end wall, said resonator having a movable collar as a part thereof, said collar having an end thereof within the resonator spaced from and opposing a part of the fixed wall of said resonator and forming thereby a constriction, said collar having an end external of the resonator, plates respectively carrying said external end of the collar and said fixed part of the resonator, springs coupling and tending to draw said plates together and lessen the spacing between said fixed part of the resonator and the collar, struts secured to one of said plates opposing the spring action and keeping said fixed part and collar spaced, said struts having greater ooemcient of expansion than said collar and automatically compensating for expansion of the collar due to heat in use and thereby maintaining the said spacing between said fixed part and the collar substantially constant under varying heat conditions encountered in use of the device, and a tuning control under one of said struts for shifting said collar irrespective of the continued functioning of the strut as an automatic temperature compensation.

3. An electron discharge device having a hollow body resonator with a fixed end wall, said resonator having a movable collar as a part thereof, said collar having an end thereof within the resonator spaced from and opposing a part of the fixed wall of said resonator and forming thereby a constriction, said collar having an end external of the resonator, plates respectively carrying said external end of the collar and said fixed part of the resonator, springs coupling and tending to draw said plates together and lessen the spacing between said fixed part of the resonator and the collar, struts secured to one of said plates opposing the spring action and keeping said fixed part and collar spaced, said struts having greater coefficient of expansion than said collar and automatically compensating for expansion of the collar due to heat in use and thereby maintaining the said spacing between said fixed part and the collar substantially constant under varying heat conditions encountered in use of the device, and a tuning lever hinged to the said plate carrying said collar, said lever underlying an end of one strut for prying thereagainst and thereby shifting said collar irrespective of the continued functioning of the strut as an automatic temperature compensation.

WILLIAM W. RIGROD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,109,880 Dow Mar. 1, 1938 2,146,365 Batchelor Feb. 7, 1939 2,183,215 Dow Dec. 12, 1939 2,251,085 U July 29, 1941 2,259,690 Hansen et a1 Oct. 21, 1941 2,311,658 Hansen et a1 Feb. 23, 1943 2,345,642 Varian et a1 Apr. 4, 1944 2,413,364 McCarthy Dec. 31, 1946 2,414,785 Harrison et al Jan. 21, 1947 2,418,844 Le Van Apr. 15, 1947 

